Star trailing issues

[Celestron4]

I have had a go at imaging M42 Orion Nebula and the result is one of my best attempts so far. However, the images seem to show some tracking/guiding issues. I have now had the same issues for a second night running and am struggling to identify the cause. I am using a Celestron Nexstar Evolution 6 SCT (with Celestron f6.3 focal reducer on a Celestron AVX mount, a 60mm guidescope and a modified Canon EOS600D. Could the issues be a limitation with the scope itself (field curvature etc) or is it likely just a guiding issue?

 

 

 

[Davey-T]

Zoomed in the stars appear to be elongated in different directions so could be a spacing problem, do they get worse with longer exposures ?

Maybe try without the focal reducer to see what shape they are.

Dave

[ollypenrice]

Doesn't look like guiding for the reason Dave identifies. Is the scope well collimated? This is normally very easy since the primary mirror is spherical.

For future reference, when tracing guiding issues it's best to begin by identifying the orientation of the camera relative to RA and Dec. When possible it's a good idea to have the camera aligned orthogonally either in Landscape (long side along RA) or portrait (long side along Dec). That way you know at a glance which axis is misbehaving and you'll also be able to repeat the framing easily in the future to add another panel or just add more data. A sort slow slew while exposing will produce a star trail showing the present orientation.

Olly

[Celestron4]

I have the Celestron SCT T-Adapter so the spacing shouldn’t be an issue. I’ll have a look at the collimation, I haven’t done it in a while so may be the issue.

[Davey-T]

2 hours ago, Celestron4 said:

I have the Celestron SCT T-Adapter so the spacing shouldn’t be an issue. I’ll have a look at the collimation, I haven’t done it in a while so may be the issue.

Once collimated SCTs generally hold collimation well, mine hasn't needed collimating for years.

I'd definitely try without the focal reducer just to eliminate it.

Dave

[vlaiv]

+1 collimation

Stars at the bottom of the image show Coma.